Effect of Nutritional Stress on the Hypothalamo-Pituitary-Gonadal Axis in the Growing Male Rat

Abstract

Background/Objective: Nutritional dwarfing (ND) consists of a decrease in weight and height gain and delayed onset of puberty. The aim of the present investigation was to study the modifications induced in male rats by the nutritional stress of a mere 20% reduction in food intake which, however, started immediately after weaning. Materials and Methods: At weaning, male Wistar rats were divided into two groups: Control (C) and ND. C rats were fed ad libitum with a balanced rodent diet. ND received 80% of the diet consumed by C for 4 weeks (T4); then they were fed ad libitum for another 4 (T8) and 8 weeks (T12). The rats were studied at T0, T4, T8 and T12 for the effects of nutritional stress and refeeding on nutritional status, body composition, hypothalamic-pituitary-gonadal axis, and sperm morphology and concentration. Results: ND body weight and length diminished vs. C (p < 0.001). ND body fat percentage decreased 40% (p < 0.001) without change in the percentage of body protein content. The hypothalamic content of LHRH did not change. However, FSH, LH and testosterone serum levels had significantly decreased (p < 0.001) at T4 in ND rats. A 48.4 % decrease in serum leptin in the ND group was observed at T4 (p < 0.05). The absolute testicular and seminal vesicle weight was significantly decreased by ND at T4 (p < 0.001). At T4 the percentage of anomalies of caudal spermatozoa increased in about 64% (p < 0.001) of ND vs. C rats, despite the unchanged sperm concentrations. All parameters normalized during refeeding. Conclusion: In this model, a decrease in leptin due to nutritional stress could be responsible, at least in part, for the inhibition of reproductive function. Refeeding normalized all parameters studied.

Hypothalamic Noradrenergic Hyperactivity and Detrimental Bone Status in an Animal Model of Nutritional Growth Retardation

“…These findings may result from diminished leptin serum levels in the present nutritional stress model as it was previously demonstrated [11]. There is considerable evidence that indicates that leptin may increase sympathetic nerve signals to brown adipose tissue, kidneys and adrenal glands, with unequivocal sympathoexcitatory actions in rodents [41,42].…”

“…In a previous study performed in our laboratory, [11] we observed inhibition of somatotrophic and reproductive axes in this nutritional stress model in post-weaning male rats that could be due, at least in part, to a decrease in serum leptin levels, an adipocyte-derived hormone linked to somatic growth, metabolism and reproduction [12][13][14]. These physiological adaptations could be considered as survival advantages during periods of sub-optimal energy intake, ensuring substrate fluxes to issues that require energy constantly (i.e.…”

Prenatal and postnatal energetic conditions and sex steroids levels across the first year of life

“…Animal models and epidemiological studies suggest that such energy differences could influence reproductive development. Among male rats, a 20% decrease in dietary energy at weaning inhibited reproductive development and reduced serum testosterone levels (Compagnucci et al 2002). Greater caloric intake has similarly been associated with higher circulating estrogen levels in adolescent girls and adult women (Dorgan et al 2003), but not adolescent boys (Dorgan et al 2006).…”

Peptides: Basic determinants of reproductive functions

“…Ewes, mice and rats subjected to restricted feeding exhibit reduced fertility. Reduced food intake decreases LH and FSH secretion and causes hypogonadotropic hypogonadism [17,28,153]. The adipose mass of an organism represents an energy storage reservoir.…”